The invention relates to a pressure sensor and a textile product including the sensor.
DE 10314211 A1 discloses a sock having a pressure sensor to measure the pressure distribution around the foot of, e.g., a diabetic patient. The measurement is used in the adaptation of a shoe to the patient's foot so as to avoid pressure peaks which would lead to tissue damage (diabetic foot syndrome). The sock includes a matrix of metallic fibers incorporated into the fabric of the sock. The metallic fibers are connected to an electronic circuit which computes the pressure distribution from the electric resistances at the intersections between the metallic fibers.
WO 2005/000052 A2 discloses a pressure sensitive input interface for an electronic device. The interface is incorporated into a textile garment and includes an array of conductive and non-conductive fibers.
It has been found that the textile pressure sensors known in the art do not allow precise measurement of an applied pressure over a sufficiently wide range. Instead, they exhibit essentially an on-off behavior where the electric resistance between the conductive drops sharply at a pressure threshold when the conductive come into contact with each other. But the resistance does not change significantly below or above the pressure threshold. Moreover, the pressure threshold is difficult to control and depends on hysteresis effects.
WO 98/33193 discloses a polymer composition showing an electrical resistivity which depends on distortion forces. The composition comprises conductive particles embedded in a non-conductive polymer.